Field of the Disclosure
The present disclosure generally relates to integrated circuit devices and more particularly to testing virtual power supplies at an integrated circuit device.
Description of the Related Art
To facilitate power management, an integrated circuit device can group its modules into different power domains, whereby each power domain employs a power grid that transfers power from the external power supply to the modules of the power domain. To reduce power consumption, the integrated circuit can individually “gate” each power grid, whereby a transistor or other switch (referred to as a power gate) at the power grid can be selectively placed in an open position in response to defined system conditions. Opening the power gate interrupts the flow of current to the corresponding power grid, thereby reducing the power supplied to the modules of the power domain.
During formation of the integrated circuit device, process variations or other conditions can cause errors in the formation of a power grid, such that the power grid's power gate is permanently placed in a closed position, an open position, or a highly resistive position. Consequently, the power gate cannot be properly opened or closed in response to the defined system conditions. However, such errors can be difficult to detect during qualification of the integrated circuit device, or can require expensive or undesirable testing circuits. For example, operation of the power grid and its associated power gate can be tested by connecting an oscillator circuit to the virtual power supply (the power supplied by the power grid) and measuring the oscillator output, but the oscillator circuit takes up a large amount of device area and can cause current leakage when the virtual power supply is power gated. The virtual power supply can also be connected to an external pin of the integrated circuit device for measurement during testing, but this requires the addition of an expensive pin to the integrated circuit device package.
The use of the same reference symbols in different drawings indicates similar or identical items.